- Forever Knight Special Effects Blood Blood in the FK universe is really undiluted Ribena, a sickenly sweet black current drink. The product is left undiluted so that it approximates the consistency of fresh blood; however, it often makes the actors sick in this form. I am told that Ribena is often available in Oriental markets, specifically grocery stores catering to immigrants from Hong Kong or ...www.loftworks.com/FK/Show_Info/special_effects.html